The desirability of preselecting one or more specific renditions from a multiple-program long-playing phonograph record, such as a 331/3 rpm L/P record, has long been recognized. This applies whether the phonograph record comprises a series of independent musical or literary, or other types of renditions, only a portion of which may appeal to the listener or only a part of which meets the purpose for which the rendition may be selected. It also applies to both home use and commercial use, including broadcasting, of phonograph records.
The manual selection of such renditions is obviously totally unacceptable, since it is imprecise and results in damage to the record and to the phonograph stylus.
The most standard form of L/P phonograph record is designed for 331/3 RPM operation and usually comprises from about 5 to 7 renditions per side for popular music and a lesser number per side for classical music. In any event, the renditions may vary in length of time and number per side of each record for any particular purpose.
Such records are usually composed of a black vinyl or other polymeric material which readily reflects light. They are usually pressed from a master die which impresses on a polymeric record blank convoluted grooves carrying a sound track emanating from the outer periphery of the record and terminating near, but spaced from its center. When a multiplicity of renditions are included on one side of the record, each such rendition is spaced from the next by a small band containing an unmodulated groove to direct the stylus of the phonograph thereacross from the preceding rendition, represented by a band of sound modulated grooves, to the next band of sound-modulated grooves. The space between the sound-modulated grooves, however, is much more responsive to the reflection of light than is the band represented by the sound-modulated grooves, thereby enabling the sensing of successive bands of sound-modulated grooves, and through appropriate means, the programming of a record player to select any one or more of such bands for reproduction.
One approach to the solution of this programming problem is represented by U.S. Pat. No. 2.952,464 to Stimler which utilizes a source of light and a photoelectric cell to detect the respective bands on the record, but which requires an auxiliary optical system including lenses wherein the source of light and reflected light are directed and reflected at angles of about 45.degree. to and from the record surface. An elaborate system of relays and switches is also employed to accomplish the desired control of the pickup arm.
The deficiencies of the system provided by Stimler are more fully pointed out in U.S. Pat. No. 3,368,080 to Nakagiri, which teaches the use of a photoelectric cell and a light emitting device, but nevertheless together with a conventional optical system, which still do not achieve the precision required, in an economical manner, for an effective system in accordance with the purposes of this invention.